Finding daily number of unique users for a Cobalt Shared Platform Product

I would like to find how many "unique" users are hitting our Cobalt Shared Platform Product. I am thinking of using PerfAPI for this. But if there is an easier way, please let me know. If PerfAPI is the way to go, I do need some help in identifying which table would hold this information. Also, can I filter out the internal users and only get this data for externals?